HOW TO BUILD A HOBBIT HOUSE FOR $100 DOLLARS
Low cost housing is one of the cornerstones of civilization
and handcrafted building projects have long been one of my passions. The day I
discovered earth bag construction was the day that I knew I could turn a dream
into a reality. My currency of construction is recycle, barter and goodwill and
the results far exceeded my expectations and, I suspect, all building codes
relating to insulation and structural integrity.
The end result is a twenty foot diameter building half dug
into a south-facing hill. Although unfinished, the inside temperature never went
below 0 C despite outside temperatures in the minus twenties – and that was
without the woodstove on. Here is how I did it.
A south-facing hill is essential as this allows you to take
full advantage of passive solar heat. A steady temperature of 55 F comes from
geothermal heat; this is because it is partially underground. An understanding
of geology, drainage and soils helps to avoid potential water problems. Ideally,
the site will be on the upper 2/3s of the slope; this gives wind protection and
avoids the cold air that gathers on low ground. The fill from the digging is
dumped around the high side, this makes it easier to fill and position the bags
of earth.
I traded backhoe time with my neighbour for hay and he
excavated a thirty-foot gouge into the hillside. The front door faces east so
the morning sun shines through the round window and two big rectangular windows
face south to maximize passive solar heat. I would have preferred the
excavation to be eight-feet deep, but we hit limestone bedrock at five feet. No
problem, the beauty of handcrafted buildings is you adapt to circumstances. I
simply added more earth to the north side and this gave the building a slightly
higher profile.
The earth bags could structurally support the roof, however,
I prefer to overbuild and the posts of the wood frame are aesthetically
pleasing and useful to anchor shelves etc. I used a line to mark a twenty foot
diameter circle and divided the circumference into eight sections. Using a
digging bar I bust down eighteen inches into the bedrock for the cedar posts. These
were then set in concrete. The centre post is 18” diameter and the outer ones
12”diameter. All the posts are braced so that they are stable during
construction.
The extended arm of the backhoe is used to lower the 8”
diameter cedar logs that connect the outer posts to the centre post. There will
be only space for three or four of these logs on top of the centre post. The
remainder lay across the first ones. All of them are spiked together using
twelve-inch nails. If these nails are not available you can make them by
cutting ¼” steel rod to length.
Nail 6” diameter cedar poles to the radial logs. These poles
are twelve inches apart. A bird’s eye view of the roof now looks like a
spider’s web. The entire roof is now covered with 1” by 6” oak boards; these
were recycled from a paddock fence.
The entire roof is first covered with two discarded farm tarpaulins;
these protect the good tarp from being punctured by the corners of the oak
boards. A trampoline deck and an abandoned inflatable raft were added to cover
the peak for good measure. Now place an undamaged good tarp over the entire
roof, I was fortunate to buy one at a yard sale. It is necessary to have a wooden
edge around the rim to hold the soil which will cover the roof. Rather than
nailing this in place and puncturing the tarp I used ‘deadman’ construction
technique to hold the timber in place. Place timber around the rim and nail the
ends together (I used old cedar fence rails), then add another circle of timber
four feet in from the rim. Join the two circles of timber together with timber.
The weight of the soil prevents this timber frame from moving. Before adding
the soil, I covered the tarp with a thin layer of old hay; this is an added
precaution in case a stone in the soil might puncture the tarp. Instead of
using regular topsoil, I covered the roof with 18” of ‘black gold’ worm
compost. This is easy to handle and greens up in jig time.
Water goes where water wants to go and it can take the
poetry out of construction. After the initial excavation I left the site for a
year and even after spring run-off there was no trickle of groundwater seeping
into the site. Following standard building practice, I dug a small trench
around all but the front of the building and laid 6” ‘O’ pipe, this will drain
any sub-surface water away from the structure.
Next, the door is fitted between the east-facing section of
the wall. Hobbit houses traditionally have round doors, mine is a triangle with
rounded sides. The door must be wide enough to allow a 5ft wide mattress
through. Deft work with the chainsaw and three curved cedar logs created the
door. So far the work has been relatively straightforward, I don’t mind admitting
that filling and positioning the bags for the walls is hard work. It takes 900
bags and they weigh up to 110lbs each. I would plan my day so that I would only
build the walls for half a day at a time. It takes about four days to do each
of the eight sections. Before starting you need to make a pounder. Set a spade
handle in an eight-inch tub of concrete; mine weighted 38 lbs and with
energetic thumping pounded the bags into rigid rectangles.
My horse farm friends donated the feed bags which otherwise
would have gone to the landfill. Each bag is filled with the sub-soil and
rubble from the excavation. Wedge the bags between the posts and pound them
tight. It is easier to fill the bags in place rather than have to haul them
into position. Stagger the joins as you would with a traditional block wall. Two
of the east-facing sections of wall and two of the south facing sections will
have window frames. The bottom of these frames is about four feet above the
ground. To build the frame for the
round, or rather, oval window, I found two tree limbs that had the same curve.
Then I cut a grove in them to fit the plate glass (originally it was a glass
table top). Fitting and position this window was the only time that I needed a
second pair of hands. There is also a 12” square frame for the woodstove pipe
and a length of 2” plastic pipe for the electric cable from the solar panel
breaker box.
It is easiest to build the back walls first and by the time
you get to fit the bags around the door and windows you will be an expert. When
the wall is two feet high, pound steel rebar through the bags, three for each
section. Continue to do this every two feet in height. This really strengthens
the wall. The handle of the pounder is about four feet long which means it gets
increasing difficult to pound the bags. The flat side of a sledgehammer does a
reasonable job of pounding until the wall is within two feet of the roof. The
final two feet I do with straw bale construction. Instead of trying to fit
bales, I double bagged loose straw and wedge these bags into position. They are
held in place by sandwiching them between 9 gauge wire fasten to the posts. The
wire is made taut by drawing it together in two places with bale twine. Any remaining gaps are filled with smaller bags
of straw. The outside of the walls are backfilled with rocks as the walls are
built.
The inside of the walls are covered with wire mesh (as used
for rabbits etc.), this holds the plaster in place. First, staple the wire mesh
to the posts and then fasten it to the bags. I made large washers out of
aluminium and hammered 4” nails into the
bags at an angle, this worked effectively. I filled the small cavities between
the mesh and the ends of the bags with strips of fabric, this saves on the
amount of plaster required.
One ton of carbon dioxide is released into the atmosphere
for every ton of cement that is manufactured.
I should have used an earth plaster, instead expediency drove me to the
dark side, winter was coming and there is no easily accessible clay on site.
The plaster was made from a hydrated lime and mortar mix of approximately 2:5
ratio. This worked well and easily adhered to the wire mesh. The first coat
just roughly covered the wire and after this had dried I applied a smooth
finishing coat. Later this was whitewashed with hydrated lime. Next summer I
will apply an earth plaster to the front of the house, in the meantime the bags
are protected from the sun with landscape fabric.
The floor was levelled and polythene vapour barrier laid
down, this was then covered with four inches of limestone screenings.
Eventually a wooden floor will be built over this. A wood cook stove stands on
the north side with the chimney going out the wall and AC electricity comes in
from a 250 watt solar panel outside. A second smaller solar panel trickle
charges a 12 volt marine battery and this powers the satellite radio. So far, I
have only built the bed: next will come bookshelves and a table. I plan to move
in early January, 2016.
